Process of purifying tantalum metal.



' without entailing the U ITED STATES WERNER v. BOLTON,

PATENT arms.

or CHARLOTTENBURG,GERMANY, ASSIGNOB to SIEMENS &' HALSKE AKTIENGESEIJLSCHAFT, OF BERLIN, GERMANY.

PnocE-ss Foe PURIFYING TANTALUM Specification of Letters Patent.

METAL- Patented Sept. 12, 1905.

Application filed October 12, 1904. fierial No. $23,207-

description.

The object of my present invention is a process for purifying tantalum metal.

Tantalum metalobtained in the known manner-for example,by reduction with sodiumusually contains non-metallic impurities, such as oxids. I have discovered that tantalum metal may be entirely freed from impurities,

especially from tantalum oxid, by heating in a suitable electric furnace the mixtures which contain the oxids. The action is probably due to the fact that the oxid. is sooner volatilized than the tantalum metal itself. The process is possibly aided by an electrolytic or thermic decomposition of the oxid into metal and oxygen.

I prefer to um, as the tantalum ture is liable to enter all known elements.

carry out this process in a vacumetal at high temperainto reaction with nearly It is obvious that a suitable inert atmosphere could .be used in which to eifect the purification if a suitable inert gas should be found. The electric arc should not be bet 'een carbon electrodes because of the liability of the formation of carbid of tantalum. ()n the other hand, metallic electrodes may be favorably employed, especially if made of tantalum metal.

The arrangement I prefer consists in pressing rods or bodies of another suitable form from the impure metal powder, or the impuremetal may be pounded in a crucible of refractory material. Such crucible may consist of magnesia or thorium oxid, lined at its inner side with a conductive coating-for example, of tantalum metal. of the impure metal. The contents of the crucible is connected to one the anode of a prevent its being melted in the electric arc serves as the cathode.

If the cathodeis large enough, it may be made of another metalfor example, silverrisk of-being melted. The described-arrangement is incloscd in a The body is made.

lead, preferably source of continuous current.- A rod of tantalum metal of suflicient size to casing connected to an air-pump and which casing consists either entirely of glass or else is provided with a spy-hole of glass. The cathode is so mounted that it may be moved in the receptacle after the vacuum has been established without destroying vacuum. The process with this apparatus is accomplished in the following way: After suflicient evacuation of the receptacle by means of the airpump the movable electrode (cathode) is brought near the tantalum mass to be treated in order to start the electric arc. The are once formed the cathode is so moved over the surface of the mass to be purified that all parts of the mass are heated successively until the tantalum metal is melted and the oxygen or oxid expelled. In this manner pure homogeneous metallic bodies free from blisters and of large size are obtained, which can easily be subjected to further treatment.

Having thus described my invention, the following is what I claim as new therein and desire to secure by Letters Patent:

1. The herein-described process of purifying tantalum, which consists in fusing the impure metal in an inert environment whereby the impurities are driven off and the metal left free. g

2. The herein-described process of purifying tantalum, which consists in fusing the impure metal in an inert environment by an electric current whereby the impurities are driven off and the metal left freefi 3. The herein-described process of purifying tantalum, whichconsists in fusing the impure metal by passing an electric current through the metal .in an inert environment pure metal in an electric furnace in a vacuum until the impurities are volatilized and drawing oif the constituents which have been volatilized by such fusing. 5, The herein-described ing tantalum, which consists in fusing the impure metal containing oxide in an inert environment whereby the impurities are-driven off" and the metal freed of oxids.

6.- The herein-described process of purifying tantalum, which consists in fusing the impure metal containing oxids in an inert environment by an electric current whereby the process of purifyimpurities are driven ofl and themetal freed of oxids.

9. The herein-described process of obtaina ing' pure tantalum, which consists in heating the impure mixture in a vacuum by means of an electric are from electrodes of, material which does not form compounds with tanta lum. f

In witness whereof I have hereunto subscribed my name this 30th day of September,

WERNER V. BOLTON. Witnesses:

HENRY HASPER, WOLDEMAR HAUPT. 

